/*
 * Copyright 2012-2021 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.boot.context.config;

import java.io.IOException;
import java.util.List;

import org.springframework.boot.context.config.ConfigData.Option;
import org.springframework.boot.context.config.ConfigData.PropertySourceOptions;
import org.springframework.boot.origin.Origin;
import org.springframework.boot.origin.OriginTrackedResource;
import org.springframework.core.env.PropertySource;
import org.springframework.core.io.Resource;

/**
 * 用于由 {@link Resource} 支持的位置的 {@link ConfigDataLoader} 实现。
 *
 * @author Phillip Webb
 * @author Madhura Bhave
 * @since 2.4.0
 */
public class StandardConfigDataLoader implements ConfigDataLoader<StandardConfigDataResource> {

	private static final PropertySourceOptions PROFILE_SPECIFIC = PropertySourceOptions.always(Option.PROFILE_SPECIFIC);

	private static final PropertySourceOptions NON_PROFILE_SPECIFIC = PropertySourceOptions.ALWAYS_NONE;

	@Override
	public ConfigData load(ConfigDataLoaderContext context, StandardConfigDataResource resource)
			throws IOException, ConfigDataNotFoundException {
		if (resource.isEmptyDirectory()) {
			// 📂 如果是空目录资源，直接返回空的 ConfigData（不加载任何配置）
			return ConfigData.EMPTY;
		}
		// ❗️ 检查资源是否存在，不存在则抛出异常（可跳过 optional 的情况）
		ConfigDataResourceNotFoundException.throwIfDoesNotExist(resource, resource.getResource());
		// 🔗 获取资源对应的引用信息
		StandardConfigDataReference reference = resource.getReference();
		// 🏷️ 用带来源追踪信息的资源包装原始资源（便于错误定位）
		Resource originTrackedResource = OriginTrackedResource.of(resource.getResource(),
				Origin.from(reference.getConfigDataLocation()));
		// 📝 构造加载时用的名称信息，用于日志和调试
		String name = String.format("Config resource '%s' via location '%s'", resource,
				reference.getConfigDataLocation());
		// 📜 调用 PropertySourceLoader（如 YamlPropertySourceLoader）加载资源，得到多个 PropertySource
		List<PropertySource<?>> propertySources = reference.getPropertySourceLoader().load(name, originTrackedResource);
		// 🧪 根据资源是否绑定了 Profile，确定 PropertySourceOptions
		PropertySourceOptions options = (resource.getProfile() != null) ? PROFILE_SPECIFIC : NON_PROFILE_SPECIFIC;
		return new ConfigData(propertySources, options);
	}

}
